Electromagnetic device.



B. LIEBOWITZ.

ELECTROMAGNETIC DEVICE.

urmoflxon FILED SEPT. 5, 1912.

Patented June 16, 1914.

2 SHEETS-SHEET l.

'B. LIBBOWITZ. ELECTROMAGNETIC DEVICE.

APPLICATION FILED SEPT. 5, 1912.

Patented June 16,1914.

2 SHEETS-SHEET 2.

f F Fig. /0.

BENJAMIN LIIlBOWIT Z, OF NEW YORK, N. Y.

nnnornomaennmc DEVICE.

Specification of Letters Patent.

Patented June 16, 1914.

Application filed September 5, 1912. Serial No. 718,753.

To all whom it may concern:

Be it known that I, BENJAMIN LIEBowrrz,

- a citizen of the United States of America,

'- pole-pieces forming an electro-magnet or electro-magnets, and a movable element of suitable magnetic material so shaped and so mounted or suspended that the air gaps between it; and said pole-pieces remain constant in len h throughout the range of positions of sai movable element. In the present forms of polarized relays and telephone receivers the movable iron element moves to and from the pole-tips of the magnets, thus causing variations in the lengths of the air-gaps, whereas in my invention the motion of the movable element is across the field ofthe permanent magnet, with no variations in the lengths of the air-gaps throu bout the range of, its positions.

Re erring to the-drawings, Figure l, is a plan view of a dia ammatlc arrangement of my invention; Flg'. 2 is a section on the line AA of Fig. 1; Fig. 3 is a side elevation of one form of polarized relay embodying my invention; Fig. 4 is a 'planview of the same; Fig. 5, is a section on the line B B of Fig. 3; Fig. 6 isa diagrammatic illustration of a telephone receiver embodying my invention; Fig. 7, is a Ian of another form of olarizedrela cm oayln myinvention; Fig. 8 is an'e' ovation oft e same,

' Figs. 9 and 10 are a plan and elevationofa modified form of the relay shown resp'ec-.

' tively in Figs. 7 and 8; Fig. 11 shows diagrammatically a modification corresponding to Fig. 1, in which the condition of con- 'stantair-gap lengths throu hout the range of the mov'a le element is 112 of motion slightly departed from, and Fig.

shows diagrammatically a Iodificahon (if my invention in which the movable element has motion of rotation about an axis perpendicular to the field.

.In Figs. 1 and 2, 101 is apermanent magnet, 102 and 102 are soft iron pole-pieces fastened to the poles of the permanent magnet, 103 is the soft iron movable element adapted to move perpendicularly to the field created by the permanent magnet between the pole-pieces 102 and 102', and 104 and 104 are coils of wire wound on ole pieces 102 and 102' respectively, preibrably in slots as'shown, or in a number of slots in the pole-pieces. The pole-pieces 102 and 102',

with their windings 104 and 104; constitute come of the oppositeelectromagnetic polarity, so that the field as a whole is strengthened between one set of pole-tips and weakened between the other. The movable element 103 is supported, suspended or pivoted in any convenient manner which will con strain it to move perpendicular to the line A A. The direct pulls of the pole-pieces 102 and 102, i. e., the pulls parallel to the line A A, on the movable element are substantially balanced, so that there is very little or no strain imposed on the support or suspension due to unbalanced forces. The movable element is made sufiiciently small in the direction of motion so as not to extend beyond the pole-pieces 102 and 102 for any position within the designed range of motion. The faces of the movable element are parallel to the faces of the pole-tips P, Q, R and S, so that for all positions within its designed range of motion the movable element will be in substantiall neutralequilibrium with respect to the fie (1 due to the permanent magnet; for it' will experience no appreciable force tending to. push it into any tips Q and R, depending on the direction of the current and the movable element experiences a force toward the denser part of the field. Suppose, for example, that due to the permanent magnet, S and R are north poles and P and Q are south poles, e., suppose fields due to the permanent magnet to pass from and R to P and Q, respectively. Suppose now a current to flow in the coils in such a direction that it tends to create a field from R to Q and from P to S. Then the field from R to Q, due to the coils will be in the same direction "as that due to the permanent magnet, whereas the field from P to S due to the coils will be opposite to that of the permanent magnet, hence the field as a whole from R to Q, will be strengthened in intensity, while the field as a whole from P to S will be weakened. Accordingly, the movable element will be impelled toward the stronger part of the field, i. 0., toward the right of Fig. 1. And if the current is reversed, the motion will also bereversed.

'Another explanation, is as follows: The re-action between a magnetic field and a coil carrying current is always such as to tend to make the total flux passing through the coil a maximum. Suppose as before that due to the permanent magnet S and R are north poles and P and Q, are south poles, and suppose a current to flow through the coils in such a direction as to tend to make P and R north poles and Q and S south poles. Now, when the movable element is in its mid-position the flux from the permanent magnet will divide substantially equally, one-half passing through coil 104 thence byway of R and Q back through coil 104, and the other half will go directly from S to P. But if the movable element moved to the right it would decrease the magnetic reluctance of the path from R to Q and increase that of from S to P, hence by so moving, the movable element would ,cause a greater total flux to pass through the coils, hence the movable element experiences a force tending to move it to the right. And if the direction of the current were reversed, the direction of the force would also be reversed.

If, instead of the coils 104 and 104 being connected so that when they are energized the pole-tips P and R tend to become of one polarity and Q and S of the opposite polarity, they are so connected that when energized they tend to make R and Q of one polarity and S and P of the opposite polarity, then the movable element, instead of experiencing a force perpendicular to the line A A will experience a couple tending to rotate it about an axis perpendicular to the plane of the paper in Fig. 1. This arrangement of the coils can be utilized-by making the faces of the movable elementwhich are opposite the pole-tips, cylindrical about an axis perpendicular to the plane of the paper suspension.

in Fig. 1, instead of plane as shown, and at the same time making the pole-tips P, Q, R and S cylindrical about the same axis, said axis being also the axis of the pivots or the Such an arrangement is diagrammatically shown in Fig. 12, which corresponds to Fig. 1. X designates the axis of rotation, which is perpendicular to the plane of the paper; the numbers correspond to those in Fig. 1. This arrangement is clearly equivalent to that shown in Figs. 1 and 2 and is regarded as being within the scope of this invention.

While it is one of the most essential features of my invention that the air-gaps be tween the movable element and the pole-tips remain constant in length throughout the range of motion of the movable element, a slight departure from this condition is also regarded as being included in my invention. It, for example, the p0letips P, Q, R, and S, and also (for best effect) the faces of the movable element, instead of being made parallel, are given a slight dihedral angle, as shown in Fig. 11, then the lengths of air gapswill not be constant through the range of motion (which in this case is assumed to be very small) of the movable element.

With such an arrangement, when the movable element is to the right of its mid-position it will experience a force to the right,

due to the permanent magnet field, and when to the left of its mid-position, a force to the left, This, of course, reduces the sensitiveness of the device, but in certainapplications, as in polarized relays, a slight holding force is sometimes desirable; The numbers of Fig. 11 correspond to those of Fi 1. This application is regarded as inclu ing only relatively small departures from the condition' of constant airgap lengths throughout the range ofpositions of the movable element.

Referring to Figs. 3, 4 and 5, I here show a form of olarized relay embodying my invention. 11 these figures, 1 is a base on which is fastened a number of permanent magnets 2 by means of the screws 3 which pass through the slots 4 in the magnets, by-

means of which slots adjustment of the permanent magnets is obtainable. 7 and 7 are coils of wire wound onthe cores 8 and 8. 9, 10, 9 and 10 are pole-tips of suitable magnetic material, as soft iron, placed on the ends of the cores 8 and 8'. 5 and 5 are supports for the cores, coils and pole-tips, which supports may be of soft iron, for example, or of permanently magnetized steel assisting the magnets 2. 6 is a cross-com necting piece of non-magnetic material to secure rigidit and alinement of the supports 5 and 5 6 is threaded to receive the screws 17 and 17'. The. coils 7 and 7 and the iron parts 8, 8, 9, 9, 10 and 10 form a pair of electromagnets. These are held in their respective sup orts and 5 by means of beveled slots in 9 and 9' fitting into corresponding slots in the supports 5 and 5. These slots permit the sliding back and forth of the electromagnets in their supports, for purposes of adjustment. This adjustment is secured by the screws 17 and 17 turning in'the arms 16 and 16' respectively, which arms are of non-magnetic material and are secured to their respective electromagnets. Collars, as shown, prevent 17. and 17 from moving in and out of their arms 16 and 16'. The electromagnets are locked in position by the nuts 18 and 18. 11 is a small soft iron block forming the movable element. It is supported by the aluminum rod 12 and the plvot-rod 13 in the pivot screws 14 and 14 which are mounted in the pivot bracket 15. The movable element 11 also carries the aluminum arm 19, which carries the movable contact of the relay. The fixed contacts are set in the contact screws 22 and 24, which are carried in the posts 20 and 21 respectively and which are locked in position by the nuts 23 and 25 respectively. 241 to 245 are binding posts to which are connected the two free terminals of the coils 7 and 7', the movable contact, and the two fixed contacts respecrespond to the soft iron pole-pieces 102 and my invention embodied in a. telephone receiver. 51 is a permanent magnet, 52 and 52 are soft iron pole-pieces, 53 is the soft iron movable element and 54 and 54 are coils wound in slots in the polepieces. These parts correspond to. 101, 102, 102', 103, 104 and 104 respectively of Figs. 1 and 2. The soft iron pole-pieces 52 and 52' are held to the permanent magnet by the screws 55 and 55 which pass through slots in the pole-pieces so that they can be moved to and from 53 for purposes of adjustment. This adjustment is obtained by means of the arms and 60 of non-magnetic material, which are secured to the pole-pieces 52 and 52 respectively and in which turn the screws 58 and 58, said screws being held in their respective arms by the collars 59 and 59 respectively. These screws thread into the permanent magnet, and by turning them they are moved in and out, carrying the diaphragm, preferably of non-magnetic maon which is fastened a number of bar-magnets 2'. At the ends of these bar-magnets are fixed the two supports 5 and 5, which are of suitable magnetic material. These supports can be made of steel permanently magnetized, and thus form part of the permanent magnet system. 7, 7 b and 7 7 are pairs of coils of wire wound on the pairs of cores 8*, 8", and 8', 8, the first pair of cores being joined by the yoke 31 and the second by the yoke 31. Shafts 33 and 33, of suitable magnetic material, slide in suitable holes in'the supports 5 and 5 and are fastened to the yokes 31 and 31' respectively. The supports are slotted to receive the thumb-nuts 34 and 34' respectively, which turn on threads on the ends of the shafts 33 and 33. Turning the thumb-screws 34 and. 34 obviously moves the ele'ctro-magnets to and from the movable element 11, thus providing the desired adjustment. 9, 10, 9 and 10 are the pole-tips of the electro-magnets. The coils, cores, yokes and pole-tips constitute two electromagnets, corresponding to 102, 104 and 102', 104 of Figs. 1 and 2. The movable element is shown at 11, with its supporting rod 12, the pivot rod 13 and pivot bracket 15, as in Figs. 3, 4 and 5. The electromagnetsare partially supported in, and prevented from turning with the thumb-screws by the brackets 32 and 32. To these are fastened the contact supports 20 and 21, the support 21 being shown partly cut away in Fig. 8 for the sake of clearness. The contact screws 22 and 24 are carried in their supports 20 and 21 respectively, and are locked in position by the nuts 23 and 25. 241 to 245 are the binding-posts as before.

In Figs. 9 and 10,1 show diagrammatically, by plan and elevation respectively, a relay similar to that shown in Figs. 7 and 8, except that only one pair of electro-magnets, 7 and 7 is employed in the modified form. The soft iron pole-tip 72 takes the place of the other pair of electro magnets. This pole-tip 72 is held in the support 73, and the electromagnet' 7 4" is supported by 71, 71 and 73 corresponding to 5 and 5 of Figs. 7 and 8. The other parts of Figs. 9 and 10 are numbered as in Figs. 7 and 8.

For relays intended for rapid operation I prefer to use laminated transformer iron in the cores, yokes, pole-tips and movable element.

By small mechanical motions in the claims is to be understood such as the movement in relays or in galvanometers or in telephone receivers. By small or slight amounts of energy isto be understood such as is necessary to operate relays or measuring instruments, or less.

By a permanent magnet is to be understood a single permanent magnet or a plurality of permanent magnets acting as a single one, or an equivalent electromagnet.

An 'electromagn'et is said to be magnetically energized, in the senseused herein, when a magnetizing current flows through the windings.

It will be seen that one of the most basic features which distinguishes my invention from others of the same class, (polarized relays, telephone receivers etc.) is that the soft iron movable element is normally in neutral equilibrium or in nearly neutral equilibrium in the direction of motion with respect to the permanentmagnet field. That is, when no magnetizing current passes through the coils, the permanent magnet exercises no force component or only a very small force component on the movable element in the direction of its motion. 'This result is achieved by having the air-gap lengths constant, or nearly so, throughout the range of positions of the movable element, and in addition, keeping the movable element within the field of-the permanent magnet at least in the direction of its motion). That is to say, the movable element is made smaller in the direction of its motion than the corresponding width of the pole-tips, so that it will always be within the field of the permanent magnet. But in certain applications, as in polarized relays, it is frequently desirable to give the movable element a bias. This can easily be done in my device by adjusting the relay so that the movable element-projects slightly outside the permanent magnet field (i. e.

slightly'beyond the pole tips) in the direction opposite to that in which it is desired to bias the relay. Suppose, for example, the movable element were allowed to project slightly beyond the pole-tips to the right in Fig. 1 then the field would tend to draw it in, i. e., to the left, hence the relay would then be biased toward the left. Only very small projections beyond the pole-tips can be used, however, as this method of biasing the relay depends on the fringing out of the lines of force atthe edges of the air-gap. The method can be improved by encouraging the fringing at the edges of the air gap, as by beveling off the outside verticaledges of the pole pieces somewhat, or by.

beveling off the'vertical edges of themovable element slightly. Hence, in general, while the most characteristic features of my invention are that the air-gap lengths remain constant throughout the range of motion and that the movable element remains always completely within the field in the direction of its motion, my invention is not to be construed as rigidly limited to these characteristics, but is to be regarded as including small departures from them.

It will be observed that there is no field passing through the middle region of the movable element, 11. 6., the region between the pole-tips. The expression within the fields therefore does not refer to this part of the movable element. And further, the extension of the movable element in a direction perpendicular to the direction of motion is not of greatdmportance as regards the operation of my device, hence the expression within the fields is to be construed as referring to the dimension of the movable element parallel to the direction of motion. That is to say, the expression the movable element is limited in its motion to remain completely within or almost completely within the fields of the permanent magnet is to be construed as meaning that the movable element is limited in its motion so that in any stage of its motion it will not project outside the region between the pole tips, or at most will project only very slightly outside this region, in the direction of its motion.

. Ihave shown my invention applied to polarized relays and to telephone receivers, butcise means herein described for utilizing the invention in these devices. The means here: in described for obtaining small mechanical motions with slight currents has the advantages of great sensitiveness and wide range of operation, and, so far as I am aware, is original with me.

I am aware that there have been prior inventions employing coils of wire, permanent magnets, soft iron pole-pieces, and airgaps between the'diiferent magnetic parts of constant length throughout the range of positions of the movable element, and I do not, therefore, broadly claim these elements in combination. But in all such prior inventions, for example the DArsonval galvanometer, the movable element is a coil of wire carrying current, whereas in my invention the movable element is a mass of magnetic material which carries no currents except the Foucault currents generated therein by the varying magnetic flux.

Therefore, I do claim:

1. A' device of the character specified, comprising a permanent magnet havlng electro-magnets associated therewith, and an armature mounted intermediate the poles for movement in a path substantially paralthe latter.

2. In a device of the character specified the combination of, a permanent magnet, a movable element disposed intermediate the poles of the magnet and movable transversely through the magnetic field thereof, said element being normally in a state of substantially neutral equilibrium with respect to the field of the permanent magnet, electro-magnet's associated with thepermanent magnet and adapted to vary the density of the magnetic field so as to cause movement of the mo\ able member in a direction depending upon the direction of the current, and means for limiting the movement of said movable elementto a path substantiall; within the magnetic field.

3. In a polarized relay, the combination I of a permanent magnet having electro-magnets associated therewith, an armature mounted to move transversely through the magnetic field in a path substantially parallelto the polar faces of the permanent magnet so as to maintain the air gap lengths substantially constant throughout the range of movement of the armature,

4. In a polarized relaythe combination of a permanent magnet hav ng electro-magnets associated therewith, an armature mounted to move transversely through the magnetic field in a path substantially parallel to the polar faces of the permanent magnet so as to maintain the air gap lengths substantially constant throughout the range of movement of the armature, and means for limiting the movement of said armature to a path substantially within the magnetic field.

5. In a relay, the following elements in combination: a permanent magnet, a support of suitable magnetic material magnetically associated with each pole of said permanentmagnet, oppositely-disposed electromagnets adjustably mounted in said supports and in magnetic relation with said supports, shaped pole-tips on said electromagnets, a correspondingly shaped movable element of suitable magnetic material supported for movement in a'path substantially parallel to the faces of the pole tips and means for limiting the movement of said element to the region between the pole tips.

- BENJAMIN LIEBOWITZ. In the presence of ARTHUR LEONARD KRENBER, HAROLD ZEAMANS. 

